The present invention relates to a high-voltage/large-current generator apparatus and a method for generating a high-voltage/large-current which can be used for exciting a plasma.
As one plasma exciting method, the following method has been known. The plasma exciting is performed by means of a high-voltage generated across a current transformer coil through which a rapidly-changed large current flows. This rapid change of the current can be obtained by commutating the coil current to a resistor so that the current from a DC power source to the current transformer coil is quickly cut off. This method, however, requires a high-power and high-speed DC circuit breaker.
Meanwhile, for actual development of a power generator or the like which is applied to a nuclear fusion process using a gas plasma, realization of a highly-reliable, high-speed and low-cost DC circuit breaker is materially important.
A vacuum circuit breaker, gas circuit breaker, semiconductor circuit breaker, and the like, are known as a DC circuit breaker. Among these, the semiconductor circuit breaker is one of most advantageous devices because it has a semi-permanent working life, high reliability, and maintenance-free features, etc. However, when a high-voltage and large-current type DC circuit breaker is to be used, the cost of the semiconductor circuit breaker device becomes very high because a large number of series/parallel-connected semiconductor elements are required.
In a plasma exciter apparatus for nuclear fusion or the like, the magnitude of a current to be flowing through a current transformer coil reaches several tens of kilo amperes to several hundreds of kilo amperes, and the magnitude the voltage generated across the both ends of the current transformer coil at the time of cutting off the current exceeds several tens of kilo volts. Consequently, to obtain a high-withstanding voltage and large current capacity, a prior art apparatus requires a large number of semiconductor elements both for a thyristor converter and a DC circuit breaker, resulting in complicating the circuit configuration of the apparatus and significantly increasing the cost thereof. This is the shortcoming of the prior art.